System for color television



3 Sheets-Sheet 1 Nov. 11, 1952 ROSE SYSTEM FOR COLOR TELEVISION Filed Dec. 17, 1949 NOV. 11', 1952 955 SYSTEM FOR COLOR TELEVIS ION 3 Sheets-Sheet 2 Filed Dec. 17, 1949 Ilka-:5 15.67

NOV. 11, 1952 A ROSE SYSTEM FOR COLOR TELEVISION 3 SheetsrSheet 3 Filed Dec 17, 1949 Patented Nov. 11, 1952 UNITED STAT'IEIS 7 SYSTEM "FOR COLORLTELEYISI O N l Albert RosaaPi-inceton, N. J assignor to Radio Corporationiof America; a-corporation .oiffDlw-z Applfcaticn December 17, 1949;i3riirl'No. 1332509 ful in--reproducing colored-images in response"- to "video si'gnals that give "simultaneous-informa tion as= to the intensities of the various compow nent colors'that maybe employed, and other embodiments" the invention is useful in repro-'-"-- du'cing'images in response to" video signals that sequentially represent the intensities of the'com ponent colors. In'all-emb'odiments', the image'is'" dire'ctly reproduced color by light producing materials such; for example; as pl'iosphors mount ed; upon orhavingthe eiiect of producing-{a single" viewing surf ace.

Coloredximages have-been reproduced in-bothsimultaneous-and sequential systems'-by-=-forming separatepartial images each of whichrepresents the intensity variation' ofa-single component color and superimposing them" b'yoptical meansonto a singl viewing screen;

When field-"or 1 frame sequential color systems havemeen employed,- the partial images may bea formed Lon ansinglelxcathode:ray :tubexand zcolor selection: obtainecli by mechanicallyeinserting ope ti'cal: lighttfilters .betwe'en .thelsurf ace :oftheitube and; theyviewer; 4 If ,1 however,: JthBJrateL'OfJ change of; color: information. is L fasterithan ;a;.v field or 1 frame rateelemental or line to line, fonexameple;,it;abecomes extremely difiicult :todevisesazsatisfactorygmechanism,forzinterposingithe colon-see lective optical filters. Furthermore, .whenxlarge imagesw are to .be formed,y ,the.mechanismzfor:

filterz insertion is often cumbersome.

In :thiswinvention, however, the'need for sepa rateikinescopes and an optical system for superimposingtheir images or the need vfor amechanism.,.for inserting optical filters is obviated whetherlthev signals are simultaneous or s-equene tial; Thislmeansithat the complexity of alcolor television receiver can be greatly reduced and that present. monochrome receivers can be adapteclnlto reproduce colored images with a mini;

mum expense. :1

One object'ofthis inveintion is to provide a noveljand'simplified system thatis capable of reproducing'images in color in. response towideo' signals that isequent-ially represent the intensity variations of different component colors in which phosphors; producingplight-of different -and cor respondingcomponent colors, may be viewed on a singlesurface;

A' further object-of =the-present invention is 'to" provide electronicapparatus functioning as a systemto-selectively'- control a cathodi' ray anovel mannner:

A further object of-tms invention -is try-provide a simplifidfi system'- capab l of reproducing images "in color from"-vi'd"eosignal-s thatsim-ult neously- =represent *the--intensi ty =variations of 'tlie: diifrent: component colors inwhich different color -'responsive phosphors may b a '-viewed one: a different suriace.--

These' -and otlier-objects of thb invention wi-ll become apparent from a detailed "considerationa of the-figures inwhich Figure-'1 is WSCHBHIHZHCSI-IOWlHg of a system' embodyingtheinvention'for-reproducing colored imagesfrom sequentially derived colored images:

Figura -1A is a*large scale view of thetarget" and-electron mirror structure of thefcathodeway tube included imFigure "-1;

Figure:2 illustrates a'tubehaving'diffrenttypa of target and:electronmirrorstructure;

Figure 12A illustrates the target. structure 10f?" Figure 2' ingreaterdetail Figure 3"illustrates the ring;multivibrator .cir- 1 cuit which may be employed'to developthe "dc.-

rivecl tube control or: keyingvvoltageiwaves Figure. 3A.?illi'1strates the waveforms that occur; in .various ."points insthelcircuitvof Figure 3 ;,-l

Figure 3B illustrates an .addingscircuitithat combines certain of the available outputs ointme t circuit showninFigureB so astoprovideaprope keyingivoltage wave;

Figure 4" illustrates a section I Of:'-' arr =electron-a mirrorinv which the rmeans sfor -creatinglawtrans=rverse electrostaticfield-icomponent: arepositioned:=

at random with respect I toithe aperture;

Figure? 51 illustrates: anotheri form pwhicl'rzthexn electron mirrorrmay assumezto-rdevelopaans elcs: ltrostatic fieldzhaving as component 'thatrisrtrans-a verse-toe thesdirection-sof approach of :thevbeamg .dotkmulti'plexsequential system;- video signals sequentially: representth'e intensities of the com ponent 1 colors and;- the-color information repros duced atany -instant of-timerepresents an el= ment of the reproducedim'age:

The cathode-*ray= tube I, an embodimentwf which is shown in Figure 1 and Figure 1A forms an important component in a combination that embodies the principles of this invention. It is, or may be, comprised of the followin standard structure, namely, an evacuated envelope which may be formed with a neck portion and a conical bulb portion as shown, an electron gun structure which may becomprised of a, cathode 2, a control grid 3 that is cylindrical in form, the cylinder being closed at one end by an apertured grid plate 4, and axially spaced tubular electrodes 5 and 6. During normal tube operation, control electrode 3 is operated at some potential negative with respect to the potential of the cathode 2', while electrode 5 is maintained at a positive potential of several hundred volts relative to the cathode potential and electrode 6 is maintained at several thousand volts positive to provide a high acceleration of the electron beam. The electrodes 3, 5 and 6, together with the cathode electrade 2 constitute an electron gun structure in which the electron emission from the cathode is formed into an electron beam. In the tube shown in Figure 1 incoming signals are applied to the negative control electrode 3 so as to modulate the density of emission of the cathode in accordance with the signals. The wall coating 1' that is deposited on the inner surface of the conical section and extended part way into the tubular section of the envelope is supplied with the same potentialas electrode 6.

The novel features of the cathode ray tube are the target [6 andv the means [8 for reflecting electronsthat pass through apertures in the target back to phosphors that lie on the target surface. This last-named surface, including the phosphors thereon, effectively emits light which is transmitted exteriorly of the tube. In this way, a luminous image in color is provided. The target IS, in this particular arrangement, is made of material having the property of electrical conductivity and has a series of apertures which may be in the form of slits that extend substantiallyparallel to one direction, for example, the horizontal direction of scansion of the electron beam. In between each of the apertures 20 and on the side of the target 16 remote from the beam projecting means, groups of different color responsive phosphors are mounted in parallel stripsv The electron mirror [8 is illustrated to an enlarged scale in Figure 1A. It is comprised of light transmitting material having the property of electrical conductivity. Ideally, it is transparent. -This mirror l8 may be constructed of fine wire mesh. The surface nearer the target I 6 of the light transmittin and electrically conductive electron mirror in the tube I, however it may be made up of suitable material, is shaped like a series of sawteeth with the center portion of the sloping face of each sawtooth approximately opposite one of the apertures 20. In this particular embodiment, equipotential lines, such as those indicated by the lines 22, 24 and 26, all slope in approximately the same direction in the region opposite each of the apertures 20. The difference in slope is not essential to this invention and is merely inherent in the form. It will be apparent to those skilled in the art that the invention is fully operable where the configuration of the mirror is such as to make the equipotential line parallel. The target I6 is held at a relatively positive potential with respect to the electron mirror l8 by a connection 2! ,to a potentiometer 29, and therefore electrons passing through the apertures 20 toward the electron mirror I8 will be reflected to one of the phosphors. The particular phosphor which is struck will depend upon the penetration of the electrons into the field between the target l6 and electron mirror 18. For example, if the electrons are permitted by field strength to penetrate to a point represented for purposes of this description by equipotential line 22, they will be reflected along a trajectory such as that indicated by numeral 28 to the blue phosphor, and if they penetrate only as far as the equipotential line 24, they will be reflected along trajectory 39 to the green phosphor. Similarly, if they only reach equipotential line 25, they will be reflected along trajectory 32 to the red phosphor. In other Words, the irregularly shaped electron mirror 18 provides an electrostatic lens opposite each of the apertures 2!] which controls the landing point of the beam on the target IS in accordance with the penetration of the beam.

The operation of the special cathode ray tube I will now be discussed in combination with a color television system of the dot multiplexed type such as described in the publication A Fifteenby Twenty-Inch Receiver for RCA Color Television System published in October 1949 and made available to the Federal Communications Commission on October 20, 1949. To obtain operation of the tube l to provide color images the means for selectively controlling this tube to be described hereinafter as part of the present invention is incorporated in the illustrative setting of the system of the publication. In that system video signals that sequentially represent the intensities of three component colors are provided by a receiver such as the receiver 38. In the embodiment of the Figure 1, these signals from the receiver 38 are applied to the grid 3 of the cathode ray tube l via a cathode follower 39 of a type well known to those skilled in the art. The rate of change from one color to another was chosen, in that particular arrangement of the publication, as 11.4 megacycles, the rate of occurrence of any single color therefore being at arate of 3.8 megacycles. The receiver 38 also supplies focusing and deflection voltages via leads 4| and 42 respectively to the focusing coil l2 and the yoke [3 in a manner well known to those skilled in the art.

The variations in penetration of the electron beam into the retarding electrostatic field between the target I6 and the mirror I8 that is required for color selection as discussed briefly heretofore in connection with Figure 1A, and to be described more in detail hereinafter, may be obtained by making the velocity of the beam different for each color. The apparatus of Figure 1 is operable to vary the control voltage applied to the electron mirror I8 and it may also operate by varying a control voltage which is applied to the cathode 2. Operation, either by cathode control or electron mirror control, is conveniently obtained by manipulation of switches 51 and 52. More in detail, beam velocity change may be accomplished by modulating the cathode 2 with a voltage wave form that changes amplitude at the same rate as the color information. For example, when the receiver 38 is similar to that shown in Figure 9 of the above publication as pointed out above, 3.8 megacycle voltage waves that are degrees out of phase with each other are derived in the receiver 38. These 120-degree phase displaced voltage waves are supplied to the grids of three ampligamers;

hers- 43; .1415 sandsd'lcoperated class fC byssuita'ble;

biasing means such,= for: examplaas bias :batteries 43-2; 45:." and Ali; Thev plates of :thesethree. ampliflers are tied to a suitable positivepotential source B+:.(not.-shown) through a commonload impedance The amplifiers 43-, 45 and lkcompriseian adderpdesignated generally by reference-character 35, which adds portions of the 120-degree phase displaced waves which are passed by the class C amplifiers; The voltage waves present at'the plates of these. amplifiers have maximum negative peaks occurring at the rate of 11.4 megacycles and arefed to an amplifier 50 which-has.

a parallel resonant circuit 31 tuned to 11.4 megac'ycles connected to its plate. The 11.4 megacycle sine wave thus derived from 3! 'is supplied to a driver amplifier 58' via an R. C. coupling network that biases this tube so that only negativepulses 40 appear at its plate; These negative pulses are 49 being clamped to ground potential by a diode 53 connected as shown. The cathode ofthe cathode follower tube 56 is connected to the cathode 2 of the cathode ray tube I and also is coupled to the-grid 3 of the cathode ray tube I via a cathode follower55, the cathodeload 51 of which is the same as-that for cathode follower 39. In order- 1' that the stepped waveform thus applied to the grid 3 and the video signals maybe clamped to asuitable negative bias, diode 59 and resistor 51 are connected in parallel between the grid and a negative point on the potentiometer 29-. In this way, the potential difference between the grid and the cathode does not vary with the application of the stepped waveform Q8 and intensity modulation of the beam in accordance with this waveform is therefore avoided. In order to obtain the 50 or 60 volt range normally required to drive a kinescope resistor 57 must be fairly large if the tubes 39' and 55 are not to draw excessive plate current. If the grids resistors were returned to ground potential, the tubes 39 and 55 would therefore be biased too heavily. For this reason, the grid resistors are returned to adjustable intermediate points on resistor 51.

When the switches 5i and 52 are in the opposite position from that shown in Figure 1 the stepped voltage waveform i8 is applied to the electron mirror is via coupling condenser 69 and is clamped to ground potential by a diode 62. When the retarding field between the mirror l8 and the target i 6 is made greater by the application of this waveform, the electrons tend to follow the trajectory 32 of Figure 1A, and as the field is reduced, the electrons penetrate nearer to the electron mirror and are therefore reflected along trajectories and 23 respectively. This method is considered to be preferable in tubes in which the capacity between the electron mirror l8 and the target i6 is so small as not to require a large power output from the source of keying signals 46.

The details of the source of keying signals 46 illustrated in Figures 3, 3A and 33 may be as follows: Three bistable multivibrators 64, 66 and 68 are connectedin a ring, as illustrated in Figure; ,3. The details.- of these multivibratorsneed not: be explained; as theyaarek-well :known fin.- the: art, but the operation of them in this particulan embodiment is as follows: Assume that the right hand tube of the multivibrator 64 is conducting and that the right hand tube of the multivibrators 6 5 andfiB are not conducting. Thismeans thatthe grid Hi is positive and thatrthe grids 72 and M are negative, The drive voltage indicated by.

the wave G of Figure 3A may be derivedat the output of driver ,as explained in connection,

with Figure 1 and when applied to thediodes 1B, 18. andfiilvia isolating condenseronly the negative portion of the waves is simultaneously applied to the grids 18, 12 and 14 at a rate of 1.1.4. megacycles; Inasmuchas: the grids 12. and

it... are. already negative enough to cut 1 off: their respective. tubes, theapplication ofthe negatives. drivevoltage has no effect ontheir associated However, the application of the I negatiyecdrive voltagev to the .grid lucausesthe multivibrators.

multivibrator fi ito flipover to itsotherstable;

conditionv and. to provide .a positivepulseto the 1 grid 72.:of..the.multivibrator 66. The grid 10 1s.. now. negative. and multivibrator tfi is the-only; one of the ring whichwill be operated on thenext negative drive .pulse because its grid fl is now positive.

The. waveforms A. through thus derived at the plates A through F of the tubes of theLmultivibrators 6e, 55 and 68 are indicated in FiguredA; and-if the waveforms available at platesD'and' E are added, the desired-wave shape 48 shown in Figuretlis obtained. An-a-dder=that may-"be used for accomplishing this: operation is shown in Figure 3B and includes two pentodes 32 and 84, theplates of which are tied to 3+ via common plate load resistor and the cathodes of which aretied to ground via a common parallel R. 0. network. If waveform D is-applied to the grid 86 of pentode 82, and waveform E is applied to the grid 88 of pentode fi L'the'wave-form' 48 is produced at the plates.

Various methods may be provided to insure that the Waveform 43 provided by the circuits of Figures 3 and 3B are in-phase with the transmitted information, but this can easily be accomplished by applying negative bias by the lead" 89to'the grids l4 and 12', and by supplyingthis same negative bias via the push button 90 (Figure 3) to the grids 9|, 92 and 10. In normal'operations, the push button is closed and the con trol grids, of all the tubes in the three multivibrators, receive the same negative bias- However,

when, it is desirable to change the, phaseof the stepped voltage wave 48 the push button 90 is opened. In this way, the right hand tubes of the,

multivibrators 56 and 68 have a negativebias on the grids 12 and 14, whereas on thevright hand tube of multivibrator 64 has a positive biason its grid 10. If then, the push button is re-.

leased at the proper time, the waveform 48 will,

be in proper phase'relationship with the video signals.

More detailedreference will now be. madeto the-operation of the special tubel in connection with Figures 1 and 1A. Whereas the aperturesand their associated phosphors, described inconnection with Figure 1, are substantially parallel to the horizontal scanning of the target, it is the voltages employed in the tube such as has beendescribed in connection: with Figures land:v

1A and the dimensions is given by the following formula:

wherein voltages are given in volts and distances in centimeters and in which:

AV:.color switching voltage Wzdimension of sawtooth or roughness L distance from apertured screen to reflector V:beam voltage ADzdefiection distance of the beam from color to color The dimensions of the apertures and phosphors is determined partly by their arrangement and partly by the amount of color resolution that may be permitted. Where they are not parallel to the horizontal scansion of the beam the situation arises where the area of the apertures lying within the beam spot is not constant as the beam proceeds across the target, and this may produce changes in intensity. Therefore, it is preferable to make the spacing between the apertures less than the spot size of the beam.

Aside from reducing any intensity variation that may be present, this reduction in the spacing between apertures interlaces the colors in a finer pattern so that the viewer may approach closer to the screen without being able to resolve the difi'erent colors and is especially advantageous on large screens.

Unless proper provisions are made, the beam will approach the target I6 of Figure 1 at different angles as it scans the raster and thus the relative spacing of the points of return with respect to the apertures 20 through which the beam entered the retarding field between the target I6 and the electron mirror is will vary. One way of insuring the normal approach of the beam to the target 5 is to make the positive potential of the target I6 on-and-one-half to two times the positive potential applied to wall coating "I. Another way of accomplishing this desired result is to curve the target I6 and the electron mirror I8 so that all points on either one are substantially the same distance from the center of deflection. In this way, the beam approaches along a radius. The relative spacing of the phosphors can be changed so that they are at the proper landing points. Then too, the slope of the sawteeth can be altered so as to change the angle of the retarding electrostatic field into which the beam is projected. In the arrangement of Figures 2 and 2A the relative potentials of the strips I00 can be suitably altered to take care of difierences in angle of approach caused by vertical deflection. The strips could be divided up in a horizontal direction and different potentials applied between successive pairs as the sides of the target are approached so as to take care of differences in angle of beam approach produced by horizontal deflection.

In the illustrated embodiments of the invention the reflected beam strikes the phosphors adjacent to the aperture through which it originally passed, but this is not necessarily the case as the phosphors may be separated from the aperture through which the beam passes originally by any desired distance with any number of apertures and groups of phosphors therebetween. In an extreme case, the phosphors could be located so that the beam does not pass between groups of phosphors but passes through apertu'res whichare all to one side of the phosphor groups before being reflected back toward one phosphor of a group. However, good results may be obtained when the distance between the point of entry into the field and the point of return of the reflected beam to the phosphors is in the neighborhood of 25 times the distance between adjacent apertures.

The electron mirror may be constructed in difierent ways. For example, as shown in Figures 2 and 2A, it may be comprised of a series of transparent current conducting plates that are located opposite each of the groups of phosphors. As an alternative to this construction, the plates I00 may be replaced by wires, but in either case, alternate plates or alternate wires are connected to relatively positive and negative sources of fixed potential. The dotted lines I02, I04 and I06 represent the type of electrostatic field that is created between adjacent plates. When the electrons penetrate such a field from an aperture they are forced downward since the positive plate is above the aperture, and if the target bearing the phosphors is positive with respect to the average potentials of the plates I00, the electrons passing through the openings 20 will be reflected to the red, green or blue phosphor, depending upon the penetration. The degree of penetration is controllable in several ways. For example, in this arrangement, the potential difference between the alternate plates I00 may be varied. The mean potential, with respect to the target ISA may be varied. The .velocity of the electron beam may be modulated. These suggested modes of operation will obtain color selection. If it is desired to vary the mean potential between the electron plat-es I00 and the target 16A, then alternate plates can be connected to the positive pole of the battery I08, the other plates being connected to the negative pole of the battery and the stepped waveform 48 may be applied to either pole of the battery. I

Although the electron mirror shown in Figures 1 and 1A has been regularly shaped and has been positioned so that corresponding points in each repeated shape are opposite an aperture, irregularly shaped surfaces may be employed such as the one illustrated in Figure 4, provided that the size of their irregularities is fairly uniform and small with respect to the aperture. In the particular arrangement, the aperture I20 is circular and surrounded by annular rings of different color responsive phosphors R, G, and B, the red responsive phosphor R being the innermost ring and the green and blue phosphors, G and B, are the other rings. Opposite the aperture I20 is the electron mirror I24 which has a series of arbitrarily positioned depressions I22 which may be substantially in the form of a half-sphere, or a portion thereof. The electrons in the beam that approach the mirror I24 along the principal axis of any of the depressions I22 will be reflected back on themselves. However, those electrons which approach the electron mirror I24 parallel to, but displaced from, the normal axis of the depressions I22 will be reflected to either the red, green or blue phosphor, as indicated by the solid line I25 and the dotted line I28. The particular phosphor on which they will impinge depends upon the penetration of the beam of electrons into an electrostatic field, the equipotential lines of which are represented by the dotted lines I29. The electrostatic field is symmetrical about the control axis of each depression that is parallel to the principal axis of the cathode ray tube.

This field may be produced by-connections 'to 'a :suitable potential source, such, for-example-as :a battery I3li.

.the, furthest will be ;reflected to the: blue phosphor' ring and those that penetrate the least will Those electrons that penetrate be reflectedto the red phosphor ring, and'similarly, those that penetrate to a region" in .be-

tween will be reflected to a green phosphor ring. Penetration may be exercised in any of theforementioned ways. The diameter of the depressions I22 may-vary, but it is essential that this diameter be small in comparison with the vdiameter of the aperture I23 if the depressions are ,to be positioned-at randomiwith respect tetheaperture.

These embodiments of certain aspects of the invention merely illustrate how color-selection .may be achieved in a tube of this type by. controlling the amount ,of penetration of electrons intoan electrostatic field having components .per-

pendicular to the direction of travel of-the beam.

For example, the electron mirror couldhave the shape indicated by Figure 5 in .which-a: series ofspikelike projections I3I are-directedfrom the electron mirror I32 towards thetarget ltll.

,The equipotential lines of the electrostatic field will ,then'be curved, as indicated. by the ,dotted .linesl36. Therefore, the electrostaticfield-has .acomponent that is transverse to the direction light in accordance with the simultaneous .variations of aplurality of component colors.

The cathode ray tube shown in Figure 6 is capable of performing these functions and is essentially the same as that shown in Figure 1,

with the exception that three separate electron gun structures, instead of one, are supplied so as to form three diilerent beams of electrons. These guns are only shown schematically in the .drawing but in the practical case should bephysically mounted in close juxtaposition so that their projectionbeams will nearly coincide. .In this way, common focusing and deflection coils may be used. Color separation is obtained by biasing the cathodes I40, I42 and I44at different potentials on the potentiometer I46-as shown. The corresponding grids are connected to the potentiometer through load resistors I ts, 459 and I52 respectively, The separation between the cathode contact and its corresponding grid. contact .at -,the potentiometer 1% is physically set ;at a fixed amount as shownby the dottedlines, and inasmuch as all these amounts are the same, the bias on each grid, with respect to its cathode, is the same. However, the cathodes I48, I64. and I42 all have different potentials and therefore the velocity of the beams projected by their respective gun structures will be sufficiently different so that they will follow separate trajectories after passing through the openings I54 in the target I56. Therefore, they will land on different phosphors in the same manner, as was explained in connection with Figure 1A. The re sistance of the potentiometer I46 is extremely small and is especially small in comparison with the values of the resistances 548, I58 and I52. The reason for this is twofold. In the first place, the grid to ground impedance will be approximately the same for each gun, and in the second place, the cathode degeneration which is produced by the beam current flowing through that i-portion ofthe potentiometer will bereduoed to a negligible amount. The sources of the' different video signals I58, I60 and I62 are respectively tied to the grids associated with cathodes I40, I42 and I44. If it weredesired-'tolxexactly equalize the grid to ground-potentialsiithe sizes of the resistors I48, I50'and' I52 couldbezsuitably altered. In a similar manner, if itwerede'sired to equalize what little cathodewdegeneration is present, resistors of suitable. sizercouldfbeiplaced inseries with each cathode'lead.

Having thus .describedrmy "inventiomrwhati is .claimed is:

1. An apparatus forreproducingimages in 'col- .or. comprisingin, combinationra"'cathode ray tube having enclosed therein: a target, groups of different color. :responsive phosphors mounted on said target, aperturesf'in said target through whichat least a portion of "-said ele'ctron beam can pass, means'for reflecting the electrons that pass: through said. apertures sothat they imping'e on one of saidphosphors, means for projecting al-beam of electrons toward said target, "and'a grid adapted to control the intensity of thebeam thus projecteda source of =vi'deosignals; thatfisequentially correspond "to the intensities or 'ferent component colors; said sourceh'aving a'n output terminal, said terminal being "connected to :said grid, a source of keying "signals" that'fa're in synchronism *with the-sequential video signals, means for applying said-keyingsignalsto therein, and difierentcolor"responsiveiphosphors mounted between said aperturesymeans forjprojecting a 'beam of-electrons through said apertures, a sourceofwaveshaving a difierent amplitude as the video signals represent different colors, means for reflecting the electrons that pass through said apertures back to asel'ected phosphor in response "to said. waves, and means for controlling the "intensity of said beam in response'torsai'd'video signals. y

3. Apparatus for reproducing images in color comprising in combination a source of video sig- 'nals thatsequentially represent the intensities of the component colors;a "cathode ray tube having enclosed therein a 'target, "apertures withinsai'd target, parallel strips of difierent color responsive phosphor associated with each aperture, means for projecting a beam of electrons toward said target, means for controlling the intensity of said beam in accordance with said video signals, a plurality of electron lenses mounted beyond said target, each of said lenses being positioned directly opposite one of said apertures, each lens being adapted to move said electrons in a direction that is transverse to said strips of phosphor, means for establishing an electrostatic field between said target and said electron lenses that reflects the electrons passing through said apertures back to said target, and means for successively establishing the magnitude of the electrostatic field at different levels in synchronism with the sequential change of said video signals.

are simultaneously presented comprising in combination, a cathode ray tube having a target,

means for projecting beams of electrons toward said target, means for individually controlling the intensity of each beam, a plurality of sources of video signals, each signal representing the intensity variations of a single color, means for applying each of these signals to one of said intensity controlling means, means for establishing the velocity of electrons in each beam at a different value, said target having a plurality of apertures through which-at least a portion of the beams can pass, a plurality of groups of phosphors mounted on the far side of said target ,from said beam projecting means, and means for reflecting all of the portions of said beam that pass through said apertures back toward said phosphors, the electrons from each beam striking a predetermined phosphor.

'7. Anapparatus for producing images in color comprising in combination a cathode ray tube having enclosed therein a target, apertures in said target, a plurality of different color responsive phosphors associated with each aperture, means for projecting a beam of electrons toward said target, means beyond said target for reflect- ,ingthe electrons that pass through said aperture with a given velocity to a predetermined phosphor and for reflecting electrons that pass through said aperture at a different velocity to another phosphor, means for controlling the intensity of said beam, a source of video signals that sequentially represent the intensity variations of a plurality of component colors, and means for varying the velocity of the electrons in the beam in synchronism with said video signals.

. 8. Color reproduction apparatus comprising in combination a cathode ray tube, a target in said tube having slits therein, lines of phosphors that produce difierent color light when struck by electrons, at least one phosphor line of each color being mounted between slits and on one side of said target, means for establishing an electrostratic field that is transverse to said slits and phosphor lines in a substantially parallel plane, said electrostatic field being of such polarity as to reflect the electrons passing through the slits back to said phosphor strips, means for projecting electrons toward said target from the side that is remote from said phosphor line, the particular phosphor line struck by the electrons that pass through said slits depending on the relationship between the velocity of said electrons and the strength of the transverse electrostatic field, and means for varying the relationship between the field and the velocity of said electrons so that the electrons may strike a desired strip.

9. A combination comprising a kinescope having an electron gun having a grid and a cathode and adapted to project a beam of electrons, a target having apertures therein mounted so as to intercept said beam, groups of diiierent color responsive parallel phosphor strips mounted on the side of. said target that is remote from said gun, and an electron mirror mounted parallel to and spaced from said target and on the side that is remote from said electron gun, means for establishing the potential of said target at a greater positive potential than said electron mirror so that the electrons passing through said apertures are reflected back to one of said phosphor strips, means for establishing the grid and cathode of said gun at a lower mean potential than said target, and means for successively changing the potential of said grid and cathode by the same amounts so as to change successively the velocity of the beam in a corresponding manner and thus cause it to strike the different phosphors in succession.

ALBERT ROSE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,988,605 Michelssen Jan. 22, 1935 2,125,599 Batchelor Aug. 2, 1938 2,264,709 Nicoll Dec. 2, 1941 2,307,188 Bedford Jan. 5, 1943 2,446,249 Schroeder Aug. 3, 1948 2,446,440 Swedlund Aug. 3, 1948 2,446,791 Schroeder Aug. 10, 1948 2,480,848 Geer Sept. 6, 1949 2,481,839 Goldsmith Sept. 13, 1949 FOREIGN PATENTS Number Country Date 866,065 France Mar. 31, 1941 

